38results about How to "Reduce current amplitude" patented technology

The invention relates to a medical instrument and discloses a transient electromagnetic field excitation system for transcranial magnetic stimulation (TMS) in the medical field, which aims at overcoming the defect that an excitation system in the prior art is large in drive current, large in pulse width, difficult in achieving a hardware circuit of the excitation system and large in hidden safety dangers. The technical scheme is that the transient electromagnetic field excitation system for TMS in the medical field comprises a power supply device, an excitation coil, a charging circuit, a discharging circuit and a control device. The power supply device is connected with the charging circuit and supplies charging current for the charging circuit. The discharging circuit is connected with the excitation coil and supplies a discharge path for the excitation coil. The control device is used for controlling startup and shutdown of the charging circuit and the discharging circuit. The transient electromagnetic field excitation system for TMS in the medical field is characterized by generating a transient electromagnetic field meeting requirements around the excitation coil by increasing current change rate to reduce magnitude of current. The technical scheme of the transient electromagnetic field excitation system for TMS in the medical field is used in the TMS excitation system, is capable of reducing complexity level of system structure, and improves system safety.

Memory cells are described along with methods for manufacturing. A memory cell as described herein includes a bottom electrode comprising a base portion and a pillar portion on the base portion, the pillar portion having a width less than that of the base portion. A dielectric surrounds the bottom electrode and has a top surface. A memory element is overlying the bottom electrode and includes a recess portion extending from the top surface of the dielectric to contact the pillar portion of the bottom electrode, wherein the recess portion of the memory element has a width substantially equal to the width of the pillar portion of the bottom electrode. A top electrode is on the memory element.

The invention discloses a 30-slot 14-pole fractional-slot double-layer short-distance distribution winding 15-phase permanent magnet synchronous motor. Fifteen phase windings are divided into three groups. The axes of five phase windings in one group are separated from one another for 72 DEG, and the five phase windings are connected for forming a five-phase star-connected symmetrical winding. The axes of the five-phase star-connected symmetrical windings which correspond with one another in the three groups are successively shifted by 12 DEG. Three natural points in the three groups of five-phase star-connected symmetrical windings are not connected with one other. The number of slots on each phase of each pole is a fractional number. The span of each coil is 2 slots. The end of the coil is relatively short, thereby saving copper and realizing small copper consumption amount. When a fundamental wave current is input into each star-connected symmetrical winding, a third harmonic current of which the amplitude is one sixth of the amplitude of the fundamental wave current can be simultaneously input. After the third harmonic current is input, not only is current amplitude of a power switch tube reduced, but also ferromagnetic saturation of the motor is reduced, and furthermore ferromagnetic material utilization rate and torque density are improved. A large-power low-speed permanent-magnet synchronous motor which is composed of a plurality of unit motors has advantages of high efficiency and relatively low vibration noise.

The invention relates to a flexible multi-level bridgeless power factor correction converter and a modulation method. The converter includes an AC inductance part, a power electronic switch network and a DC capacitor part; a diode D 1 The anode is connected to the switching tube S 1 Drain, switch tube S 1 The source is connected to the switching tube S 2 Drain; Diode D 2 The anode is connected to the switching tube S 3 Drain, switch tube S 3 The source is connected to the switching tube S 4 Drain; switch tube S 5 The source is connected to the switching tube S 3 Source; switch tube S 6 The source is connected to the switching tube S 1 source; diode D 1 Cathode and Diode D 2 The cathode is connected; the switch tube S 2 source and switch S 4 The source is connected; the switch tube S 5 drain and switch S 6 connected to the drain. It can reduce inductance loss and volume, reduce on-state loss at low input voltage, have smaller DC capacitance, and have higher power density; it can flexibly realize five-level and seven-level operation without changing the circuit structure state switch.

The invention relates to a single-phase and five-level boost type power factor correction converter, which comprises a diode single-phase full-bridge rectifier circuit, a boost inductor L, a power electronic switch network, a series capacitor network and a parallel resistor network. The boost inductor L is connected between the direct-current positive pole of the diode single-phase full-bridge rectifier circuit and the first end of the power electronic switch network. The second end of the power electronic switch network is connected with the direct-current negative pole of the diode single-phase full-bridge rectifier circuit. In this way, on the premise that a switch frequency and a maximum allowable inductor current ripple are kept consistent, the volume of the boost inductor is reducedby about 75%, and the total volume of the converter is greatly reduced. Or, on the premise that the output power, the switch frequency and the inductor volume are kept consistent, the amplitude of theinductor high-frequency ripple current is reduced by about 75%. The heating of the inductor is greatly reduced, and the efficiency of the converter is improved. The voltage stress of a switch tube can be reduced by about 50%, and the cost is reduced.

The invention provides a deadbeat direct torque control method of a switched reluctance motor, comprising the following steps: calculating the position angle of the rotor through a photoelectric encoder, and calculating the flux linkage and current of the motor in a rotating coordinate system; The error with the feedback torque and the given flux linkage and the three-phase voltage and current in the stator coordinate system; calculate the space voltage vector in the rotating coordinate system for controlling the operation of the motor in the next beat; obtain six pulse signals to control the motor. The present invention directly controls the torque and flux linkage by controlling the two-phase reference voltage in the rotating reference coordinate system, and controls the flux linkage and torque within one control cycle, so that the torque ripple is smaller and the flux linkage is also significantly reduced .

Disclosed is a direct current capacitor harmonic current suppression method. Back-to-back converters are adopted; the active direct current link capacitor current in the back-to-back converters is from superposition of direct currents of a rectifier i<dcr> and an inverter i<dci>; the phases of harmonic components in the two currents i<dcr> and i<dci>are determined by the relative phase PWM carrier waves of the rectifier and the inverter; and by actively controlling and regulating the frequencies and phases of PWM carrier waves in the rectifier and the inverter, the direct current link harmonic currents from the two converter levels can be the same in phases, so that the capacitor harmonic current minimization can be achieved. By adoption of the direct current capacitor harmonic current suppression method provided by the invention, harmonic contents and current amplitudes in the first and second carrier frequency bands in the direct current link capacitor current can be obviously lowered; and by virtue of the method, the power supply mass specification can be satisfied and capacitor current harmonic can be effectively reduced without using a high-capacity direct current link capacitor.

The invention relates to a differential-noise-reduction-based SICM voltage modulation imaging device and method. The device comprises a voltage driving unit, a current detecting unit, a signal modulating unit, a feedback control unit and a mechanism executing unit. In addition, the method includes the flowing steps that: a signal generator generates two paths of co-frequency alternating current voltages, wherein one path of voltage is connected to a patch clamp amplifier to serve as a driving voltage and the other path of voltage is connected to a lock-in amplifier to serve as a reference voltage; capacitance compensation is performed by the patch clamp amplifier; one path of modulation voltage having the same frequency and same phase as the reference signal is connected to the lock-in amplifier to carry out feedback signal modulation; calculation is carried out to obtain a new current setting value; and the lock-in amplifier feeds back an extracted current component to a controller, adistance between the probe and the sample is controlled, a track of the relative displacement of the probe and the sample is recorded, and thus image scanning is completed. According to the invention, the feedback signal is modulated to increase the amplitude of the driving voltage, so that the signal-to-noise ratio of the system is improved and thus the Z-direction resolution ratio and the scanning speed of the SICM system are improved.